Sure wish you could put up even a fake surveillance camera... and whenever you see him, grap a real camera and use the flash and make sure he sees you ...take his picture... it really does make ppl wonder what you are doing. Why not take the note back to his doorway, saying he must have meant it for a neighbor of yours. Even a little bit of assertiveness on your part will make him think, because he doesn't expect YOU to do anything. If you really want to get his goat, schedule REALTORS to come by and look over your home, make friends with one and make an agreement.... have them come by, maybe come around to the side yard or something, stay a moment and then leave...

ok maybe I still have too much of a fever to be giving advice... but surely I gave you thoughts? Stay safe.